Planetary Imaging - What am I doing wrong?

[peje]

Using a modded (IR filter removed) Canon 40d with BYE's planetary imaging module. No matter what settings I try the image is blown out. I've attached a screenshot showing 1/8000 @ ISO100 and it's still blown out. Please ignore the pink colour, probably down to the filter removal.

 

I'm clearly doing something wrong but cannot figure out what

 

Thanks in advance,

Pete

[s3igell]

Planetary Mode is "nominally" VIDEO (well actually Individual Frames snagged from the LiveView SDK Video Feed that are then re-combined into an AVI Video) - and at even only 10fps any attempt to record the Full Resolution of the 18MP Sensor would result in MASSIVE Data Rates which would overwhelm the Transfer and Storage limits of the Camera / USB2 / File Format.  

Let's do a little Math:

 

5184w x 3456h x 48bit = 51843456 bytes (49.5MB)

 

495MB per sec @ 10fps

 

The original AVI 2GB Filesize Limit would allow only 4 sec of "Full Resolution / Full Bitdepth / Uncompressed" Video.

 

Now, AVI is NONE of those - it is Reduced Bitdepth (usually 4-6bit/Color) and Compressed AND nowhere near Full 18MP Resolution.  Planetary Videos are usually VGA (640x480) or maybe (1024x768) or FullHD (1920x1080) or at most 4K UHD (3840x2160).  And to produce ANY of these, the Full FOV of the Sensor is Downsampled (Interpolated) rathern than Cropped.

 

So, after all the Math:  The "5x Zoom LiveView" of BYE Planetary Mode is about the BEST Resolution AVI that you are going to Find from a DSLR.

[peje]

Planetary Mode is "nominally" VIDEO (well actually Individual Frames snagged from the LiveView SDK Video Feed that are then re-combined into an AVI Video) - and at even only 10fps any attempt to record the Full Resolution of the 18MP Sensor would result in MASSIVE Data Rates which would overwhelm the Transfer and Storage limits of the Camera / USB2 / File Format.  

Let's do a little Math:

 

5184w x 3456h x 48bit = 51843456 bytes (49.5MB)

 

495MB per sec @ 10fps

 

The original AVI 2GB Filesize Limit would allow only 4 sec of "Full Resolution / Full Bitdepth / Uncompressed" Video.

 

Now, AVI is NONE of those - it is Reduced Bitdepth (usually 4-6bit/Color) and Compressed AND nowhere near Full 18MP Resolution.  Planetary Videos are usually VGA (640x480) or maybe (1024x768) or FullHD (1920x1080) or at most 4K UHD (3840x2160).  And to produce ANY of these, the Full FOV of the Sensor is Downsampled (Interpolated) rathern than Cropped.

 

So, after all the Math:  The "5x Zoom LiveView" of BYE Planetary Mode is about the BEST Resolution AVI that you are going to Find from a DSLR.

 

This is the bit I was missing! Thankyou so much for adding the final piece to the jigsaw

[admin]

You probably have exposure simulation turned off in your camera menu.  Turn it on and try again.

 

Regards,

[peje]

Will give it a try next time. Would this stop the camera from using the settings I chose?

[admin]

Yes, it will.

[peje]

Excellent. Roll on some more clear skies!! Too close to bedtime now LOL

[peje]

Another question on the 5x zoom...

 

is this 5x width and height seperately? as in when you click it you will see one '25th' of the full size? Going by what I seen last night this sounds about right but wouldn't be 100%

[astroman133]

Normally, the LCD display on the back of the camera is smaller (fewer pixels across and down) than the camera's sensor, so the resolution of the image has to be reduced to display the entire image on the LCD display.  The 5X zoom feature displays the portion of the image at the Zoom rectangle at full resolution of the camera sensor. This is approximately 20% of the entire image.

 

Since BYE is displaying the same image that the camera would be displaying on the LCD, you see the targeted part of the image at full resolution when using the 5X zoom.

[peje]

Sorry if Im being slow on the uptake here, my end goal is to figure out a value for my FoV at 5x zoom.

 

Would the easiest way be to take a photo and use the resolution to determine the FoV?

[astroman133]

5X zoom is only used for Planetary imaging.  The planet will still be much smaller than the 5X Zoomed FOV, so why do you care?

 

You could get a decent approximation by calculating the FOV of the unzoomed image and then divide both the width and height by 5.  The accuracy of the result will depend on whether the 5X zoom is actually 5.00X and not 4.97 or 5.03X.

 

You don't need to take an image to get the FOV, you just need to do the math using your scope's focal length and the size of a single pixel and the size of the sensor..

[peje]

Sorry I must not have worded my questiom very well. My query is,

 

Does 5x zoom mean 1/5 (20%) of the area

 

OR

 

1/5 of the width x 1/5 of the height? This being 4% of the area.

[astroman133]

And I probably confused you even more due to the error in my calculations.

 

I meant to say that the 5X zoom shows 20% of the area which is ~45% of the height and ~45% of the width of the full image.

 

Sorry for any confusion.

[peje]

Not to worry, its a Friday night so there are more pressing things for the grey matter than maths!

 

Thanks for the info

[astroman133]

Well, I got out my T5i and it appears that I am wrong again. Your original supposition appears to be correct.  The Zoom box is about 1/5th the width and 1/5th the height of a full frame.  This makes the zoomed image 1/25th of the total frame size.

 

The raw images from my T5i are 5184 x 3456.  The JPG files from a Planetary capture are 1249 x 832. I used BYE to collect this sample images and extracted these numbers from the EXIF data. This means that the planetary JPG files are about 24% of the height and 24% of the width of the full frame, not 20% as expected.

 

So 5X appears to be a nominal value not an exact value. However, I do believe that these 5X images are at the full sensor resolution regardless of how the numbers work out.

 

Once again, sorry for the confusion! I'm glad that you asked the question because I learned something.

[peje]

Oh this is interesting, I didn't pick up on the full resolution things earlier. They can't be full sensor resolution, the reason for this that optically the same light lands on the sensor no matter what digital zoom you are at. There is no way for the sensor to spread this light across the sensor making the outer pixels 'see' the data that would normally be directed to the inner pixels.

 

I'm just going to boot up my astro PC now and get some figures I got from my 40d, once BYN supports 5x I will be able to get this data also.

[peje]

OK so here's the numbers for the 40d:

 

RAW     3888 w  x  2592 h

JPEG (5x)     768 w x 800 h

 

So that gives:

 

W(jpeg) = 20% W(raw)

H(jpeg) = 30% H(raw)

[astroman133]

Sorry, but there is no "digital zoom" involved in the 5X zoom and that is the whole point.

 

Forget about BYE for a moment and consider only the camera. The LCD display will not display data from the entire sensor at the full resolution of the sensor. Your sensor has 3888 pixels across. The LCD display has less. So in order to display the image on the LCD display the image must be shrunk to the resolution of the LCD display. With the 5X Zoom, a small portion of the image is displayed on the LCD display at full resolution.  There is no zoom going on, despite the name. What is happening is that most of the image is cropped out and only the area within the zoom box is displayed and there is a 1:1 ratio between the sensor pixels and the LCD display pixels.

 

When BYE is connected, the LCD image is simply downloaded to BYE.

 

Your numbers show that the RAW image has an aspect ratio of 3:2.  This is a normal photographic aspect ratio.  Your JPEG, however, does not have a 3:2 aspect ratio.  It is more like 1:1.04.  Interesting!

[peje]

OK I don't really disagree with anything you say, the difference between digital zoom and the 5x is basically that 5x doesn't stretch after the crop.

 

My point was that 5x cannot produce a 'full resolution' image, as I type this it clicked...if the image was stretched to full sensor resolution then it would become digital zoom. What would be the advantage of this stretch anyway, it wouldn't create more data, it would just pixelate the image.

 

I'm finding this conversation very interesting so thanks for that!!

[astroman133]

I still don't think that you get it. 5X is showing a portion of the full image at full resolution, where 1 pixel on the display is showing 1 pixel from the sensor.

 

By stretching I guess that you mean zooming. If you zoom in to greater than 100% then the display program simply makes the sensor pixels larger and you begin to get pixelization.

 

So let me say it again...If the entire image, or part of the image, is displayed at full resolution it is not zoomed. When you are looking at an image on the LCD display you are zoomed out.  At 5X you are unzoomed and at 10X you are zoomed in.

 

I hope this makes more sense.

[peje]

Maybe something just clicked, when you say 'full resolution' do you mean the full resolution of the screen or the sensor?

 

What I'm saying is that you cannot have the 5x portion at full sensor resolution, unless you stretch the image, which we don't.

[astroman133]

I mean full resolution of the sensor.

 

Let me say it a different way...At 5X, the camera takes a portion of the full image that will just fit on the LCD screen without zooming in or out and that is what is displayed.

[peje]

You can't have the 5x at the full resolution without stretching, it's not optically possible. If stretched, it is digital zoom.

 

"At 5X, the camera takes a portion of the full image that will just fit on the LCD screen without zooming in or out and that is what is displayed" - I agree completely, this will be at the LCD screen resolution not full sensor resolution.

 

It's getting late here so I think we should just leave it as we disagree LOL. I do appreciate the debate though

[admin]

You can't have the 5x at the full resolution without stretching, it's not optically possible. If stretched, it is digital zoom.

 

"At 5X, the camera takes a portion of the full image that will just fit on the LCD screen without zooming in or out and that is what is displayed" - I agree completely, this will be at the LCD screen resolution not full sensor resolution.

 

It's getting late here so I think we should just leave it as we disagree LOL. I do appreciate the debate though

 

This is not necessarily true; the LCD screen size is irrelevant to 5x zoom.

 

5X zoom is simply a sensor crop, your get a 1:1 pixel resolution of the cropped area... meaning 1 pixel on the 5x crop = 1 pixel on the image.

[peje]

This is not necessarily true; the LCD screen size is irrelevant to 5x zoom.

 

5X zoom is simply a sensor crop, your get a 1:1 pixel resolution of the cropped area... meaning 1 pixel on the 5x crop = 1 pixel on the image.

I was thinking about this 1:1 this morning. Why is this an advantage? Surely a normal picture is 1:1 between sensor and final image? Or am I missing some internal processing step

[astroman133]

You are correct, for a normal picture, but LiveView frames are intended to be displayed on the LCD display, even if they are sent to the PC, instead, and therefore have a reduced resolution.

 

You did this test yourself when you compared the size of a normal, full-sized RAW image compared to a LiveView JPG frame. The JPG frame contained way less data than the RAW. This is what I mean by lower resolution.

[admin]

I was thinking about this 1:1 this morning. Why is this an advantage? Surely a normal picture is 1:1 between sensor and final image? Or am I missing some internal processing step

 

Because you get the absolute best image quality this way because the image has not been rescaled up or down.  An image looses a lot of quality with each rescale so a 1:1 pixel resolution image will yield better detail.

[peje]

Thanks guys.